Shanghai has gone green in the lead up to the opening of the World Expo today. Not in the environmental sense, although urban sustainability is a lynchpin of the Expo slogan “Better City, Better Life”. Rather, topping off a year of ambitious demolition, construction and renovation there is now a frenzy of flower planting.

The plants take up precious space on Shanghai’s crowded pavements and climb the walls surrounding building sites. Don’t look too closely though: some of the flora is plastic.

Shanghai has spared no expense for its big Expo moment. China is famously imprecise when it comes to admitting what it has spent on public projects. The official Expo budget is just over $4bn (€3bn) but the figure being talked of around the city is $40bn (€30bn) for the total spend.

That includes the Expo site, city redevelopment and infrastructure, free tickets and public transport for all of the city’s 20 million residents – and pavement flower boxes. Even excluding the price tags of the nearly 200 individual national and private sector pavilions at the Expo, Shanghai has outspent Beijing whose 2008 Olympics cost an estimated $30m to $44m (€22m to €33m).

Other expenses include the wholesale facelift of the city – every building in the city centre got a fresh coat of paint and matching covers for their ubiquitous air-conditioner units. The waterfront walkway facing the iconic Bund closed for almost a year for renovations and the Garden Bridge to its north was temporarily removed for repair.

Shanghai’s overhaul goes beyond the cosmetic: eight new subway lines have been laid in recent years. The Pudong International Airport got a second terminal and the domestic Hongqiao Airport was revamped too.

Since winning the 2010 Expo bid in 2002, advertising for the Expo has been ubiquitous. Countdown clocks dot major intersections and images of the red China pavilion and the cheesy bright blue mascot Haibao have overwhelmed at least 40 per cent of advertising space in Shanghai. “I can fall asleep and see Haibao and the China pavilion tattooed on the back of my eyelids,” jokes journalist and Expo commentator Adam Minter.

Haibao, resembling a big dancing cartoon condom, attracts popular ridicule but all criticism of its design, or the Expo itself, is verboten in the Chinese press. And there is much to criticise: the cost, the dubious sustainability theme for a 5.3 sq km site that will be demolished after six months, and the suppression of local culture. Authorities have pressured Shanghainese to abandon their traditional habit of public pyjama wearing, condemned historic neighbourhoods deemed unsightly, banned street vendors and cracked down on the independent arts, censoring bands and harassing music venues.

However, bloggers have had a field-day. “Haibao makes my head hurt,” writes iconoclastic Shanghainese writer Han Han, whose blog is among the world’s most read. He has also suggested that several Shanghainese should be displayed as works of art in the China pavilion. Preferably wearing pyjamas.